1. Field of the Invention
The present invention relates to a monopolar and to a bipolar electrode for a urological resectoscope.
2. Description of Related Art
Resectoscopes are mostly used foremost for prostate resections, though, depending on the particular design, they also may be used for other surgical purposes. Herein the concept of xe2x80x9cresectoscopexe2x80x9d denotes endoscopic instruments wherein an optics and a monopolar or bipolar electrode-support, together with one or two distal electrodes, for instance a resecting and a neutral electrode configured in a stem tube. Further, the electrode support together with the electrodes are configured in an axially displaceable manner and are affixed at its proximal end to a resectoscope slide block with which it makes electric contact. The slide block is axially displaceable by manually driving a grip in order to axially displace the electrode.
During prostate resection, the resectoscope is advanced by its distal stem tube end through the urethra inside the prostrate. When hf is applied to the electrode, this electrode may be advanced and retracted by manually driving the slide block in order to cut tissue. Generally, the electrode is configured as a wire loop to trim tissue snippets. Furthermore, the electrode may assume other geometries, for instance being a button electrode, a roller electrode, a knife electrode or the like, in order to allow application to different purposes such as coagulation, cutting or the like.
Classical resectoscopy makes use of the monopolar or unipolar technology. Therein an hf current is set up between the resection electrodexe2x80x94the active electrodexe2x80x94through the patient""s body and a neutral electrode of comparatively large surface externally affixed to the patient, for instance to his thigh.
However, the electric current through the patient""s body entails risks that cannot be totally excluded even when the resectoscope is handled expertly. For instance, there are uncontrollable leakage or drift currents which, if the patient were to touch metal, for instance that of the operational table, may result in painful skin burns. Also, as regards current-induced muscle contractions, there is the danger the patient may move suddenly in an uncontrolled manner whereby he might be cut by the resectoscope. There is always some danger that muscles or nerves in the vicinity of the resection zone shall be damaged at least temporarily by drifting currents.
The above cited risks may be nearly entirely eliminated when using bipolar techniques. All such techniques offer the feature that not only the active electrode, but also the neutral or return electrode, are inserted into the body of the patient. As a result of this, the hf current is set up only between the two electrodes at the electrode supportxe2x80x94but not, or merely over defined, short paths, through the body of the patient. Such a bipolar electrode is disclosed in the German Offenlegungsschrift 25 21 719 wherein, therefore, the electrode support is crossed by two electrical conductor wires.
It is also known, with respect to bipolar electrodes, to replace the neutral electrode with a second active electrode acting as the return electrode, the electric current being set up between these two electrodes each of which makes contact with the tissue. Such a bipolar electrode is shown in the patent document WO 96/234449.
However, both the monopolar and bipolar electrodes incur the problem of properly setting up electrical contact between the conductor wires feeding an electric current to the electrodes and their contact zones in the slide block. There the electrical connection or contact must be set up using extension cables leading to the output terminals of a separately set up hf generator. HF-loaded contact sites are problematical and tend to defects such as charring.
In older designs, a tightening screw simultaneously sets up the contact and the mechanical affixation of the electrode support inside the slide block. Once such a contact site chars, the entire slide block must be replaced.
A monopolar design of this kind is known from FIG. 3 of each of U.S. Pat. Nos. 4,917,621 and 4,919,131. The slide block is fitted with a continuous transverse cavity accepting the plug of the hf extension cable to contact the bared contact zone of the electrode support in this cavity. A clamping element acting on the affixation zone of the electrode support is configured distally relative to the cavity.
This design offers the advantage of separately mechanically affixing the electrode support and the clamping element on the slide block, as a result of which it is possible to first check this slide block""s appropriate mechanical operation. Thereupon contact may be implemented with the plug. If the contact site should char, only the electrode support and the cable together with the plug need be changed. The clamping element and the slide block, on the other hand, remain intact because the clamping element is separate.
However, the known design of the above species has drawbacks. Because the affixation device is configured distally from the contacting element, the electrode support site where affixation takes place is crossed by the electric conductor connecting the contacting site to the active electrode. As a result the electrode support lacks mechanical strength in this region. The affixation device must allow for this lack of strength and, illustratively, may only operate with minute tightening forces. If affixation takes place by means of a slide block entering a groove and acting on the electrode support, then the groove may only be very shallow and consequently the reliability of affixation shall be considerably reduced.
The proximal end zone of the electrode support is constituted by the zone wherein affixation takes place and by the contacting zone. Therefore, these zones, namely the full end zone of the electrode support, are rigid and more resistant to bending than the remainder of the electrode support, which consists only of an inner conductor and an outer insulation. In resectoscopes, however, the electrode support typically will be configured tightly against the optics inside the stem tube, whereas, in the region of the slide block, the support and optics must be farther apart in order to subtend enough space for the contacting system and the affixation device. Therefore, the electrode support must be pivotably supported inside the main block in the manner indicated, for instance, in FIG. 13 of the patent document WO 96/234449. Since the main block is required to be of moderate length on technical grounds, substantial pivoting must take place over a short path. However, such pivoting motion is hampered by the considerable length of the rigid end region of the known electrode supports.
Moreover assembly may be defective if the electrode support was insufficiently inserted and thereupon was fixed in place and contacted.
With reference to FIG. 16 of the patent document WO 96/234449, which includes a bipolar electrode, the electrode support is fitted with two contact zones in the region of the slide block. An extension cable plug, which can be affixed to the slide block, sets up contact with both contact zones, which it furthermore clamps onto. This design does not provide a separate, special affixation element. Therefore, this design precludes affixing the electrode support to test mechanical operation before contacting takes place.
An objective of the present invention is to create an improved, monopolar or bipolar electrode of the above species, allowing to affix the electrode support in the slide block and to set up an electrical connection or contact with both steps being implemented in problem-free manner.
In accordance with the preset invention, the electrode support of the electrode is separate from the affixation zone and is configured proximally relative to the first contact zone. Accordingly, as regards the resectoscope""s slide block, the affixation element must be proximal relative to the first contact element.
As a result of this design separation, the electrode support must be mechanically separately affixed by means of the affixation element on the slide block whereby its appropriate mechanical operation may be tested in a first step. Thereupon, a plug may be applied to set up electrical contact. If the contact zone should char, then only the electrode support jointly with the cable and plug need be exchanged. The clamping element and the slide block remain intact because the clamping block is now designed separately. This electrode design moreover offers the advantage that the affixation zone of the electrode support no longer is crossed by an inner conductor and consequently may be designed for high mechanical strength. A number of different highly reliable affixation methods may be used, for instance clamping by applying high clamping forces, locking into deep grooves or even locking by means of a pin through a transverse borehole in the electrode support. Furthermore, highly retentive snap-in connections may be used. Another advantage offered by the proximal configuration of the affixation zone is that, assuming proper affixation, the electrode support is entirely inserted. That is, the electrode support""s contact zone is configured at the site of the contact element and, hence, electrical contacting can be set up. Lastly, the problem of pivoting the rigid end zone of the electrode support during insertion into the main block may be very effectively solved. The bending-resistant end piece consisting of the contact zone and the affixation zone may be shortened. The electrode support""s affixation zone also may be designed with a lesser diameter, thereby enabling tighter pivoting.
In further accordance with the present invention, and with respect to a bipolar electrode, the affixation zone is configured apart from both contact zones and proximally to at least one of them. In this manner it is possible to first test the appropriate mechanical operation before setting up electrical contact by means of a plug.
The electrode of the present invention, on one hand, makes it possible to configure the first contact zone proximally and to mount the second one distally from the affixation zone. In corresponding manner, the affixation element should be configured between the two contact elements in the slide block. Advantageously, only one inner conductor would cross the affixation zone and thereby a higher clamping force might be applied to the affixation zone. This feature also would facilitate insulating the two contact zones because they already are being separated by the affixation zone when affixation zone is made of an insulating materials such as a non-conducting ceramic.
In further accordance with the present invention, two contact zones are configured distally relative to the affixation zone. In this case and with respect to the resectoscope""s slide block, the affixation element is disposed proximally relative to the two contact devices. Such an electrode design offers the advantage in that neither inner conductor crosses the electrode support""s affixation zone and, thus, the affixation zone may be designed for very high mechanical strength. In this manner the affixation advantages discussed hereinbefore with reference to a monopolar electrode can be achieved. Another advantage offered by the affixation zone""s proximal configuration is that, assuming a proper affixation procedure, the electrode support is reliably fully inserted and, therefore, the electrode support""s contact zones are also situated at the sites of the contact elements, whereby contacting free of defects may take place. Furthermore, the problem encountered with pivoting the stiff end segment of the electrode support during insertion through the main block can be very effectively solved. The bending-resistant end piece consisting of the two contact zones and of the affixation zone then may be shortened, however the insulation between the two contact zones must be preserved. The electrode support""s affixation zone also may be designed to be of a lesser diameter, as a result of which guidance by a tighter pivoting motion is improved.
In further accordance with the present invention, the affixation zone is wholly separated from the remaining design of the electrode support in order to attain good affixation. A solid and continuous metal design may also be selected.
The affixation zone and at least part of an adjacent contact zone may be integral. As a result, the design is simplified with respect to manufacture and greater mechanical strength is attained. When both contact zones are situated distally from the affixation zone, then, according to the invention, at least the proximal part of the contact zone adjacent to the affixation zone shall be made integral, with the affixation zone. When the affixation zone is situated between the two contact zones, then selectively either the distal portion of the contact zone proximally adjacent to the affixation zone shall be integral with the affixation zone, or at least the proximal portion of the contact zone, which is distally adjacent to the affixation zone is integral with the affixation zone.
In further accordance with the invention, the affixation zone is made of an electrically insulating material if it is configured between the two contact zones. In that case the affixation zone contributes to insulated length and thereby allows shortening the electrode""s proximal end.